Alkyl-cycloalkyl phenols and rubber compositions including same as antioxidants



' perature.

ALKYL-CYCLOALKYL PHENOLS AND RUBBER COMPOSITIONS INCLUDING SAME AS jAN TI- OXIDAN TS Arthur Lambert and Gwyn Eifion Williams, Blackle'y, Manchester, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application October 5, 1953 Serial No. 384,335

Claims priority, application Great Britain October 16, 1952 6 Claims. (Cl. 260-4585) This invention relates to new chemical compounds and to their manufacture and application as rubber antioxidants.

The said new compounds are 2-a-alkylcycloalkyl-4z6- dimethylphenols in which the alkyl group has not more than 4 carbon atoms and the cycloalkyl group is cyclopentyl, methylcyclopentyl, cyclohexyl or methylcyclohexyl.

We manufacture the compounds by interacting in the presence of an acid catalyst, 2:4dimethylphenol and an a-alkylcycloalkene in which the alkyl group has, as before, not more than 4 carbon atoms and the cycloalkene is cyclopentene, methylcyclopentene, cyclohexene and methylcyclohexene.

2:4-dimethylphenol is conveniently obtained technically in admixture with the isomeric 2:5-dimethylphenol. It can if desired be combined with the alkylcycloalkene without first separating from the 2:5-isomer.

The new compounds are powerful antioxidants with excellent non-staining properties. As is well known many otherwise excellent antioxidants have the defect of staining white or light-coloured rubber vulcanisates and this defect makes them unsuitable for use in the manufacture of many kinds of rubber articles. Considerable attention has been directed in recent years to the search for new antioxidants which shall be free from this defect and as a result several so-called non-staining antioxidants have been discovered.

However, these antioxidants normally produce some detectable difference in shade; thus a mixture yielding a white vulcanisate without the antioxidant will give a cream one with it.

With the antioxidants of the present invention even this diflerence is avoided and in general they produce no alteration in the appearance of the-vulcanisate-i The new antioxidants may be used in natural and synthetic rubbers and are also adapted for addition to latices of both natural and synthetic rubbers. They are employed in the manufacture of rubber articles according to the usual methods. Thus they may for example be mixed with rubber along with vulcanising or other ingredients and the resulting mixes then cured by heat treatment. They are effective in proportions of about A; to 2 percent of the weight of the rubber.

The synthetic rubbers which may be used include for example polymers of butadiene-1z3- and 2-chlorobutadiene-1:3- and copolymers of either of these compounds with acrylonitrile, styrene, methyl methacrylate and other well-known polymerisable compounds which can be used in the manufacture of these rubbers.

The following examples in which parts are by weight illustrate but do not limit the invention.

Example 1 A mixture of 24.4 parts of 2:4-dimethylphenol, 19.6 parts of s-methylcyclohexene and 1.23 parts of sulphuric 2,839,493 Patented June 17, 1958 2 acid (S. G. 1.84) was stirred for 16 hours at room tem- The product was dissolved' in 200 parts of benzene, washed 3 times with 50 parts of 10% aqueous sodium carbonate and distilled. After removal of the benzene, 2-u-methylcyclohexyl-4:6-dimethylphenol was obtained as a colourless oil 13. P. 178-180 C./22 mm.

It crystallised from light petroleum (B. P. 40-60 C.) M. I. 28-29 C.

Example 2 Rubber mixes of the following compositions were made up:

A, parts B, parts Pale crepe rubber 100 100 Zinc oxide 1 10 1O Barytos 75 Stearic no 1 1 Titanium dioxide. 10 10 Sulphur 2 2 Zinc diethyldithioearbamate 0.375 0. 375 2-a-M ethylcyclohexyl-dzG-dimethylphenol 1 The rubber mixes were vulcanised in a press for 12 minutes at 125 C. and then submitted to accelerated ag ing tests in the conventional manner in the oxygen bomb (70 C. and 300 lbs/in. oxygen pressure) and in the air oven at 100 C.

The results were as follows:

Tensile Elonga- Tensile Elonga Strength, tion at Strength, tion at kg./sq.cm. break, kg./sq.cm. break,

percent; I percent Uuaged 211 726 200 710 Aged 8 days bomb, Perished" Perished 149 618 300 p. s. 1'. 02 at 70. 12 days bomb do do. 124 633 16 days bomb do do 99 510 Aged 16 hours air 111 631 134 610 oven at 100 0. Aged 32l1r's. air 84 624 101 608 oven at 100 C. Aged 48 hrs. air 55 593 647 oven at 0.

Samples of the vulcanised rubber were exposed for 6 weeks to sunlight, with the following results:

A B Light cream Light cream Example 3 To a stirred mixture of 45 parts of 2:4-dimethylphenol and 2.76 parts of sulphuric acid (S. G. 1.84), a-ethylcyclohexene (18.6 parts) was added dropwise so that the temperature did not exceed 30 C., themixture was then stirred for 16 hours at room temperature, heated at 60 C., with excess 10% aqueous sodium hydroxide, cooled and extracted with ether. The extract was washed with 10% aqueous sodium hydroxide, water and dried over anhydrous sodium sulphate. After removal of the ether, 2-e-ethylcyclohexy1-4:6-dimethylphenol was obtained as a colourless oil, B. P. 176l78 C./l3 mm.

The formula of the compound is as follows:

OH CEHE oHio-o==o-o-onioHi uill-0 011 CHa-CHz-CH:

Example 4 A mixture of 40 parts of 2:4 dimethylphenol, 1.84

. .umu

' 2,839,493 a 4 parts of sulphuric acid (S. G. 1.84) and 28 parts of a-n: bomb (70 C. and 300 lbs/in. oxygen pressure). The butylcyclophexene was treated exactly as described in results were as follows:

A B C D E Tensile Elonga- Tensile Elonga- Tensile Elonga- Tensile Elonga- Tensile Elonga- Strength, tion at Strength, tion at Strength, tion at Strength, tion at Strength, tion at kg./sq. break, kg./sq. break, kg./sq. break, kgJsq. break, kgJsq. break,

. percent crn. percent 7 em. 7 percent cm. percent cm. percent Unaged 179 596 199 637 191 628 198 i 628 198 546 Aged 8 days bomb, 300 17 89 152 530 149 528 155 525 121 477 p. s. 1. O: at 70 0."- 12 days bomb; perished. perished. 123 628 111 583 103 558 84 516 16 days bomb do -do. 92 608 92 577 103 580 79 554 Exposure 12 weeks to N stain same as No stain same as No stain same as No stain same as sunlight. blank. blank. blank. blank.

Example 3. 2-a-n-butylcyclohexyl-4 6 dimethylphenol What we claim is:

was obtained as a colourless oil, B. P. 100 C./0.03 mm. 20 1. 2-alpha-alkylcycloalkyl-4:6-dimethylphenols inwhich It crystallised from light petroleum (B. 6080 C.), the alkyl substituent has not more than 4 carbon atoms M. P. 57-58 C. and the cycloalkyl substituent is selected from the group Example 5 cogsistilzlg lof lzyfilopelntyl, methylcyclopentyl, cyclohexyl r an me ycycoexy.

A mixture 015.50 Parts of 2:4 dlmethylphenol 2. 2-alpha-methylcyclohexyl-4:G-dimethylphenol. parts.of sulphunc acid 1'84) and part? of 3. Process for the manufacture of 2-alpha-alkylcyclot-y-d1methylcyclohexene was treated exactly as described alkyhh6 dimethylphenols in which the alkyl group has m Example 2'w'y'dlmethylcyclhXyL4:6'd1methyl; not more than 4 carbon atoms and the cycloalkyl sub- Phencl W S obtamed colourles s 188E190 stituent is selected from the group consisting of cycloi 3 9 3 5 5? from hght'petroleum 30 'pentyl, methylcyclopentyl, cyclohexyl and methylcyclohexyl, WhlCh comprises Interacting at from substantially Example 6 room temperature up to about 30 C., in the presence of an acid catalyst, 2:4-dimethylphenol and an. alphaalkylcyeloalkene in which the alkyl group has not more than 4 carbon atoms and the cycloalkene is selected from the group consisting of cyclopentene, methylcyclopentene, cyclohexene and methylcyclo-hexene.

4. A rubber composition comprising a rubber selected from the group consisting of natural rubber, synthetic 40 rubbers selected from the group consisting of polymers Example 7 of butadiene-l,3 and 2-chlorobutadiene-1,3 and copoly- Rubber mixes of the following Compositions we mers thereof with acrylonitrile, styrene and methyl methmade up: acrylate, and having one of the 2-alpha-alkylcycloalkyl- 4:6-dimethylphenols of claim 1 incorporated therein, said composition being characterized by its age-resistance.

5. A rubber composition as claimed in claim 4 comprising from A to 2%, by weight of the rubber therein,

A mixture of parts of 2:4-dimethylphenol, 1.84 parts of sulphuric acid (S. G. 1.84) and 20.5 parts of oc-methylcyclopentene was treated exactly as in Example 3. 2-a-methylcyclopentyl-4:6-dimethylphenol was obtained as a colourless oil, B. P. 160-l64 C./16 mm. It crystallised from light petroleum (B. P. -80 C.), M. P. 46-47 C.

gif i f 28 i8 i8 28 of the 2-alpha-alkylcycloalkyl-4:6-dimethylphenol. lsstaegtgs m i i i i 6. A rubber composition, as claimed in claim 4, Where- Titaniurndioxide: ..III 10 10 1o 10 10 50 in said rubber is in the form of latices. Sulphur 2. 5 2. 5 2. 5 2. 5 2. 5 ljztr iggfiggg%ffifiggigfigg%% 5 References Cited in the file of this patent 1 UNITED STATES PATENTS nol 201-1111 butylcyelohexyl 4:6-dimethyl- 1 1,917,823 Britton a a1 July11,1933

2,248,827 Stevens et al. July 8, 1941 2,567,848 Kooyman Sept. 11, 1951 OTHER REFERENCES The rubber mixes were vulcanised in a press for 10 60 Wegler et al.: Makromol, Chem. 9, 1-24 (l952),

minutes at 141 C., and then submitted to accelerated abstracted in Chemical Abstracts, Vol.48, pp. 640-64l ageing tests in the conventional manner in the oxygen (1954). r 

1. 2-ALPHA-ALKYLCYCLOALKYL-4:6-DIMETHYLPHENOLS IN WHICH THE ALKYL SUBSTITUENT HAS NOT MORE THAN 4 CARBON ATOMS AND THE CYCLOALKYL SUBSTITUENT IS SELECTED FROM THE GROUP CONSISTING OF CYCLOPENTYL, METHYLCYCLOPENTYL, CYCLOHEXYL AND METHYLCYCLOHEXYL. 